Limit switch actuator



Sept 16, 1958 s. BURROWS 3 9 LIMIT SWITCH ACTUATOR Filed April 2, 1956 sSheets-Sheet 1 filfiurrows p 9 1958 s. BURROWS 2,852,630

LIMIT SWITCH ACTUATOR Filed April 2, 1956 I 3 Sheets-Sheet 2 S. BURROWSLIMIT SWITCH ACTUATOR Sept. 16, 1958 3 Sheets-Sheet 5 Filed April 2,1956 United States Patent LIMIT SWITCH ACTUATOR Stanley Burrows,Dukinfield, England, assignor to Joseph Adamson & Company Limited, Hyde,England, a British company Application April 2, 1956, Serial No. 575,422Claims priority, application Great Britain April 4, 1955 Claims. (Cl.200-47) This invention has for its object to provide improved means foractuating limit switches on electrically operated cranes, for shuttingoff the drive to the drum or barrel when the rope or chain is fullywound thereon.

According to the invention, the limit switch operating means includes ashaft carrying two gear wheels having different numbers of teeth, onebeing fixed on the shaft and the other loose, both meshing with a singlepinion which is rotatable in a housing driven by the drum or barrel, theshaft being normally stationary so that the loose gear wheel is rotatedthereon as the housing revolves, and the gear wheels having parts whichengage with one another after a given number of revolutions of thehousing, whereby the shaft is turned to operate the limit switch.

The housing may be mounted on an extension piece secured to the barrelshaft. The gear wheels may have numbers of teeth differing by one, andmay each have a dog or stop on the side which faces the other wheel, toenable the one wheel to lock with the other when the dogs come intocontact. Since the pinion is then in mesh with two locked gear wheels ofslightly different pitch, it also becomes locked on its axis, andfurther rotation of the housing causes the locked assembly of pinion andwheels to revolve about the axis of the housing.

The shaft may have any convenient means for actuating the limit switchwhen the shaft is turned, such as a disc having cam surfaces adapted toengage a switch lever for opening or closing the switch, according tothe direction of rotation of the shaft. The shaft may be held in itsnormal position by the switch lever which may be weighted or springloaded so as to press the cam against a suitable stop.

When the shaft and cam disc are reversed so as to reset the switch afterit has been operated, the cam is returned to normal position by theweighted or spring loaded lever.

With this arrangement the limit switch can be reliably operated, and canbe re-set by a small reverse movement of the barrel.

Referring to the accompanying drawings:

Figure 1 shows in section a limit switch operating gear in accordancewith the invention.

Figure 2 shows one application of the gear to a limit switch.

Figures 3 and 4 show alternative applications.

Referring to Figures 1 and 2, a flanged boss 1 is keyed to a barrelshaft 2 or an intermediate shaft of a crane. Secured to the flange is acasing 3 in which is mounted a pin 4 on which a pinion 5 is rotatable. Ashaft 6 running in bearings 7, 8 in the casing 3 has a spur wheel 9keyed to it, and another spur wheel 10 is rotatable on the shaft 6. Thewheels 9 and 10 both mesh with the pinion 5, and the wheel 9 has onetooth more than the wheel 10. There are stops 11, 12 on the wheels 9, 10which come together when the wheels turn relatively to one another. Onthe end of the shaft 6 is a flange 13, to which is bolted a 2,852,630Patented Sept. 16, 1958 cam 14. The cam 14 has for example 12 bolt holeswhile the flange 13 has 14 holes, bolts 15 being inserted in twodiametrically opposite holes, so that the cam may be adjusted in steps 55 revolution of the shaft .6. The cam 14 has a recess 16 in its flange,which receives a lever 17 pivoted at 18 and having a pin 19 engaging theoperating lever 20 of a limit switch 21. Figure 2 shows the lever 17 inits tripped position in broken lines.

Figure 2 shows the application of the gear to a limit switch having aspring-actuated lever 20 which presses against the pin 19 of the lever17 causing the latter to hold the cam 14 in the position shown until thecam turns in a counter clockwise direction, causing the limit switch tobe tripped.

As the barrel shaft 2 turns the casing 3, the pinion 5 is rotated by thestationary spur wheel 9 and drives the wheel 10 until the stops 11 and12 make contact. Since the pinion 5 is then in mesh with two locked gearwheels of slightly different pitch, it becomes locked on its axis, andfurther rotation of the casing 3 causes the shaft 6 and cam 14 torotate, and the limit switch 21 to be operated to stop the windingmotor. The number of turns of the barrel shaft 2 required to trip theswitch 21 depends on the initial angular distance between the stops 11,12 and this is adjusted by adjusting the position of the cam 14 withrespect to the flange 13. For example, if the wheel 9 has 60 teeth, thegear can be adjusted to trip the switch 21 after any number of turns ofthe barrel shaft up to 55 turns.

The method employed for setting the gear is to set the hoist gear of thecrane to the position at which tripping of the switch is required tooccur, turn the cam 14 in the hoisting direction of the barrel until thegears lock, then release the cam from the flange 13 and turn the cam tothe position in which it trips the switch and finally bolt the cam tothe flange 13 in that position.

Figure 3 shows an alternative arrangement in which the lever 17 isconnected by a link 22 to the operating arm 23 of a switch 24, the arm23 being connected by an adjustable link 25 to the operating arm 26 of asecond switch 27. The cam 14 turns anticlockwise to trip the switcheswhen the barrel has turned through the desired number of turns. Theoperating levers 23 and 26 have weights 28, 29 for resetting theswitches.

Figure 4 shows another arrangement, in which the lever 17 operates aswitch lever 30 of a switch 31, by means of a link 32, lever 33 and link34. In this case the weight 35 extends at right angles to the switchlever 30.

What I claim is:

1. Means for operating limit switches on an electricallyoperated crane,for shutting off the drive to the drum or barrel when the rope or chainis fully wound thereon, comprising a housing adapted to be rotated bythe crane drum, a shaft rotatable in the housing, a first spur wheelfixed on the shaft, a second spur wheel rotatable on the shaft andhaving a smaller number of teeth than the first spur wheel, parts on thespur wheels adapted to engage one another as one wheel turns relative tothe other, a pinion rotatably mounted in the housing and engaging bothspur wheels, the shaft and the first spur wheel remaining initiallystationary, and the second spur wheel being rotated on the shaft as thehousing revolves until it engages the first spur wheel and drives saidfirst spur wheel and the shaft, and a means fixed on the shaft, adaptedto actuate a limit switch when the shaft is turned.

2. Means as claimed in claim 1, in which each spur wheel has a stopmember on the side facing the other spur wheel, adapted to engage thestop member on the other spur wheel when one wheel turns relative to theother.

3. Means as claimed in claim 1, in which the shaft 3 v 4, carries a camdisc for actuatinga limit, switch; when, the that .the-numher of: turns;to. bemade byzthe barrelbefore shaft'is turned. the switch -is trippedcan be adjusted.

4-. Means as claimed in claim 1, having acamdisc fixed on the shaft, aflange on the cam disc with a slot References Clted m the file of thispatent :therein, and a switch-operating lever engaging the slot, 5UNITED STATES PATENTS the shape of the lever allowing the cam disc totut-n in- 2,255,574 Waseige Sept. 9, 1941 one directiononly. 2,348,987Lock May 16, 1944 5. Means as claimed in claim 1, in which the switch2,356,167 McKelvey Aug. 22, 1944 actuating means is adjustably seemed onthe shaft, so 2,495,917 Miner Jan. 31, 1950

